Rise is vertical
Measure the height difference. For a run of steps, measure the overall rise rather than assuming every step is equal.
rise = run ÷ ratioMEASURE · UNDERSTAND · PLAN
A better route starts
with the right measurements.
Turn a rise and a slope into a useful ramp plan. See the horizontal run, the sloping surface and the space for rest landings. Then check the details against one named reference.
02
Your route, explained
ISO 21542:2021Calculate a plan to see the dimensions and checks.
Horizontal runSloped portions only
Gradient
Sloping surfaceExcludes level landings
Total riseBetween finished surfaces
Unfolded side view
Layout concept
Flight-by-flight dimensions
| Flight | Rise | Run | Surface |
|---|
What the measurements tell us
Before this becomes a build
Survey the complete route, door manoeuvring space, edge protection, handrails, surface, drainage and structure. Resolve site conditions and local requirements with a qualified designer. A slope calculation cannot certify accessibility.
03
A gentler slope needs more room
The same rise can produce very different routes. Compare horizontal runs first; flight limits and landings can add more space. The table follows the current total rise.
| Slope | Gradient | Horizontal run | Try it |
|---|
Three lengths. Three different jobs.
Run is horizontal
A 1:20 slope needs 20 units of horizontal travel for each unit up. Do not measure along the ramp board and call it the run.
run = rise × ratioSurface is sloping
The surface is the hypotenuse of the triangle. Level landings are additional surfaces with their own clear-space requirements.
surface = √(rise² + run²)Gradient (%) = 100 × rise ÷ run · Angle = atan(rise ÷ run) · 1:20 = 5%, not 20°.
Built from named references
This is an original A11y.mv tool. Its geometry is independent of a standard; its dimensional checks are deliberately tied to one reference at a time.
ISO 21542:2021
The ISO profile uses the supplied 2021 edition, clause 6.4 and Table 6, for new-construction ramp dimensions. Between listed gradients, it conservatively uses the next steeper listed row and limits both run and rise. It does not interpolate. Existing-building exceptions are outside this profile.
ISO's legal adoption depends on the project. The licensed source PDF is not distributed with this site.
ISO publication record ↗ADA 2010
The ADA profile uses §§403 and 405, with US customary dimensions converted exactly (1 in = 25.4 mm). It does not mix the standard's rounded metric equivalents into calculations. Existing-site exceptions and curb ramps require a separate assessment.
ADA ramp requirements ↗Access Board ramp guide ↗
Tool and practical references
The linked tools informed the choice of inputs, comparison views and practical route questions. Manufacturer examples are useful context; dimensional checks here come from the selected standard.
Continue with the whole-building accessibility guide or the measurement lesson and field method.